Smart antenna technology is directed to antennas having the ability to change radio beam transmission and reception patterns to suit the environment within which radio communication systems operate. Smart antennas have the advantage of providing relatively high radio link gain without adding excessive cost or system complexity.
Smart antenna technology has been used in wireless communication systems for decades, and has recently been investigated for use in wireless local area networks (WLANs). In a WLAN, a client station (CS) is a device used by a mobile end user for communication with other stations within the same WLAN or with other entities outside of the WLAN. Central hubs that provide distribution services in WLANs are referred to as access points (APs). Access points are similar to base stations in wireless telecommunication systems.
A client station can be equipped with a smart antenna as well as an antenna steering algorithm that enables the antenna to switch electronically to a particular directional antenna beam. This enables the client station to communicate with its access point while achieving high performance.
For a client station operating in a WLAN, available signal conditions may often be sufficiently degraded when viewed in all directions using an omni-directional antenna. However, the signal may be received when directional selectivity is used. Fine-combed scanning of every direction, using steerable or beam formed smart antennas, is possible but can be very costly in terms of both hardware/software implementation and beam searching or beam forming processing time.
A need exists to enable client stations to perform in these conditions without having to finely scan the environment. Example scenarios where this condition may exist include interference that is dominant in one direction and the desired signal source is present in another direction, at the edge of a coverage area (or in a hidden node) where the signal may be very weak and present only in a very limited direction, and zones of destructive multipath combination when all angles are observed and where the paths are widespread in angle.